Battery pack

ABSTRACT

A battery pack comprises a plurality of battery modules and a holding spacer which holds the battery module. A plurality of projections are provided on the holding spacer. The projections contact the battery module to hold the battery module and form a flow path for a coolant. A heat generating structure is embedded in the holding spacer or inserted into a hollow section of the holding spacer. In a cold climate, electricity is applied to the heat generating structure, to heat the battery module.

PRIORITY INFORMATION

This application claims priority to Japanese Patent Application No.2008-320430, filed on Dec. 17, 2008, which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a battery pack in which a plurality ofbattery modules each having a plurality of cells are stacked with a gaptherebetween, and in particular, to a battery pack in which a spacer forholding a battery module is placed between adjacent battery modules.

2. Description of the Related Art

In the related art, there is known a battery pack wherein a plurality ofbattery modules each having a plurality of cells are placed, and aspacer is placed between adjacent battery modules. The battery pack is,for example, a secondary battery (such as a nickel-metal hydride batteryor a lithium ion battery) which is used as a power supply of an electricvehicle and a hybrid electric vehicle.

FIGS. 9-11 show a structure of a battery pack disclosed in WO2006/087962 A1. FIG. 9 shows a structure of a holding spacer 130 whichforms a part of the battery pack, FIG. 10 shows a structure of a batterymodule 110, and FIG. 11 shows a state of being assembled into a batterypack. A holding spacer 130 which holds the battery module 110 is placedbetween adjacent battery modules 110. The battery module 110 and theholding spacer 130 are overall constrained by two end plates (endboards) 180 and four constraining rods 185, to become an integratedstructure. In addition, the battery module 110 and the holding spacer130 are held by a first spacer support member (upper case) 160 and asecond spacer support member (lower case) 170. The first spacer supportmember 160 and the second spacer support member 170 are fixed by a bolt173 and a nut 175.

Each battery module 110 has an approximate rectangular parallelepipedshape including two opposing long side surfaces 110 a and 110 b, twoopposing short side surfaces 110 c and 110 d, and two opposing endsurfaces 110 e and 110 f. The battery module 110 comprises a plurality(in the figures, eight) of cells 111 which are placed in one line. Thecells 111 are connected in series with a safety valve facing toward aside of the short side surface 110 c. An upper cover member 113 whichcovers each safety surface and which forms a gas discharge path with thecell case is placed on the side of the short side surface 110 c of thecells 111 connected in series. In addition, a negative electrode sidecover member 115 is placed on the side of the end surface 110 e of theplaced cell 111, and a positive electrode side cover member 117 isplaced on the side of the end surface 110 f. An external negativeelectrode terminal 116 which protrudes to the outside of the module isprovided at an approximate center of the negative electrode side covermember 115, and an external positive electrode terminal 118 whichprotrudes to the outside of the module is provided at an approximatecenter of the positive electrode side cover member 117. A discharge hole119 is provided at an upper section of the positive electrode side covermember 117, which is in communication with the gas discharge path formedbetween the upper cover member 113 and the cell cases.

The holding spacer 130 is placed between the battery modules 110 to holdthe battery module 110, and forms, between the battery module 110 andthe holding spacer 130, a cooling path through which a coolant iscirculated. The holding spacer 130 comprises a spacer body 131 having anapproximate plate shape and which is directly interposed between thebattery modules 110. In the spacer body 131, a plurality of first modulesupport sections 133 which support the short side surfaces 110 c of theadjacent battery modules 110 are provided on an end in a verticaldirection Z. In addition, in the spacer body 131, a plurality of secondmodule support sections 135 which support the short side surface 110 dof the adjacent battery modules 110 are provided on the other end in thevertical direction Z. The battery module 110 which is mounted on theholding spacer 130 is placed between the first module support section133 and the second module support section 135, so that movement in thevertical direction Z is restricted. Moreover, in the spacer body 131, aplurality of third module support sections 137 which support the endsurface 110 e or 110 f of the battery modules 110 that are placedadjacent to each other are provided on one end in a direction ofplacement X of the cells. In addition, in the spacer body 131, aplurality of fourth module support sections 139 which support the endsurface 110 e or 110 f of the battery modules that are placed adjacentto each other are provided on the other end in the direction ofplacement X of the cells. The battery module 110 mounted on the holdingspacer 130 is placed between the third module support section 137 andthe fourth module support section 139, so that movement in the directionof placement X of the cells is restricted. Moreover, in the spacer body131, a plurality of cooling path forming projections 141 are provided inorder to form a cooling path for circulating coolant between long sidesurfaces 110 a and 110 b of adjacent battery modules 110. The coolingpath forming projection 141 projects in a direction of placement Y ofthe module and extends in a straight line shape in the verticaldirection Z. The long side surfaces 110 a and 110 b of the batterymodule 110 mounted on the holding spacer 130 contact the cooling pathforming projections 141, to form the coolant path between the long sidesurfaces 110 a and 110 b and the spacer body 131. A first elastic member143 and a second elastic member 145 are formed with rubber, and preventfree movement of the holding spacer 130. A plate-shaped rubber member147 is held on the holding spacer 130 in a state where the rubber member147 is elastically deformed in the direction of placement Y of themodule and elastically contacts the long side surface 110 a or 110 b ofthe battery module 110. With this structure, the battery module 110 iselastically held by the holding spacer 130.

On the other hand, when the temperature is low, the output of thebattery pack is reduced and sufficient performance cannot be achieved.In consideration of this, a technique has been proposed in which thebattery pack is heated when the automobile is run under a very coldenvironment. For example, JP 2003-223938 A discloses a battery device inwhich a plurality of secondary batteries are heated by a sheet-shapedheat generating structure which uniformly generates heat over the entiresurface.

Although provision of the sheet-shaped heat generating structure whichuniformly generates heat over the entire surface is effective when thebattery pack is to be heated in a cold climate, with a structure ofsimply adding the heat generating structure, the number of components isincreased and the structure becomes more complex. Therefore, a structureis desired to reliably heat the battery pack in the cold climate and toachieve superior performance of the battery pack while maintaining thealready-existing structure of the battery pack as much as possible.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided abattery pack comprising a plurality of battery modules, and a holdingspacer which is placed between the battery modules and holds the batterymodule, wherein, in the holding spacer, a plurality of projections whichcontact the battery module and hold the battery module are formed, acooling path through which a coolant is circulated is formed in a partwhere the projection is not formed, and a heat generating unit whichheats the battery module is provided.

According to another aspect of the present invention, it is preferablethat, in the battery pack, the heat generating unit is embedded in theholding spacer.

According to another aspect of the present invention, it is preferablethat, in the battery pack, a hollow section is formed in the holdingspacer, and the heat generating unit is inserted into the hollowsection.

According to another aspect of the present invention, it is preferablethat, in the battery pack, the heat generating unit has a greater amountof heat generation at a periphery section of the battery pack than at acenter section of the battery pack.

According to various aspects of the present invention, because the heatgenerating unit is provided in the holding spacer itself, it is possibleto reliably heat the battery module and prevent performance degradationunder low temperature in a cold climate or the like without increasingthe number of components. The holding spacer of various aspects of thepresent invention has a holding function for the battery module, acooling path forming function, and a heating function for the batterymodule.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a battery pack according to a preferredembodiment of the present invention.

FIG. 2 is a partial enlarged view of FIG. 1.

FIG. 3 is an outer appearance view of FIG. 2 viewed from direction B.

FIG. 4 is an A-A cross sectional view of FIG. 2.

FIG. 5 is a diagram showing another structure of a holding spacer.

FIG. 6 is a partial perspective view showing another structure of theholding spacer.

FIG. 7 is an outer appearance view of FIG. 6 viewed from direction D.

FIG. 8 is a C-C cross sectional view of FIG. 6.

FIG. 9 is a perspective view of a holding spacer of related art.

FIG. 10 is a perspective view of a battery module.

FIG. 11 is a diagram schematically showing a structure of a batterypack.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the present invention will now be describedwith reference to the drawings.

FIG. 1 shows a structure of a battery pack in a preferred embodiment ofthe present invention. The outer appearance shape is similar to that ofthe battery pack of the related art shown in FIG. 11, and a holdingspacer 130 which holds battery modules 110 is placed between the batterymodules 110. A cooling path through which a coolant is circulated isformed between the battery module 110 and the holding spacer 130. Thebattery module 110 and the holding spacer 130 are integrally restrainedby two endplates (end boards) 180 and four restraining rods (orrestraining bands) 185 to form an integrated structure. As shown in FIG.10, each battery module 110 has an approximate rectangularparallelepiped shape with two opposing long side surfaces 110 a and 110b, two opposing short side surfaces 110 c and 110 d, and two opposingend surfaces 110 e and 110 f. The battery module 110 comprises aplurality (in the figures, 8) of cells 111 which are placed in one line.The cells 111 are connected in series with the safety valve facingtoward the side of the short side surface 110 c. The followingadvantages can be achieved by such a structure with a rectangularparallelepiped shape of the battery module 110 and the holding spacer130, and in which the components are integrated by sandwiching both endswith end plates and with restraining rods 185 or the like. Because arectangular parallelepiped-shaped (flat sheet-shaped) battery module 110and a rectangular parallelepiped-shaped (flat sheet-shaped) holdingspacer 130 are bound and pressured in the stack direction, the thermalresistance between the battery module 110 and the holding spacer 130 issmall, and a more significant effect can be achieved when a coolant pathforming projection 141 to be described later is used as a heatconduction structure. In addition, because the heat exchange between thecoolant and the holding spacer 130 when the coolant passes through thecooling path is facilitated, this structure is effective in increasingthe in-vehicle temperature using the coolant discharged from the batterycell. Moreover, because the holding spacer has a flat sheet shape, asheet-shaped heat generating structure can be effectively used.Furthermore, an area of each coolant path forming projection 141 whichcontacts the battery module 110 can be reduced, and thus the degree ofload of each cooling path forming projection 141 can be reduced and aprojection placement design which is optimized with regard to heat canbe easily employed.

The holding spacer 130 is formed with a resin having an electricalinsulating characteristic, and is placed between the battery modules 110to hold the battery modules 110, and a cooling path through which acoolant is circulated is formed between the battery module 110 and theholding spacer 130. In the related art, the holding spacer 130 has sucha function of holding the battery module 130 and the function of formingthe cooling path. In the present embodiment, in addition to thesefunctions, the holding spacer 130 also has a heating function touniformly heat the battery module 110 and prevent reduction inperformance when the environment temperature of the battery module 110is low and less than or equal to a predetermined temperature.

FIG. 2 is a partial enlarged view of FIG. 1. The holding spacer 130comprises a spacer body 131 and the cooling path forming projection 141.The cooling path forming projections 141 project in a direction ofplacement of the module and extend in a straight line shape along adirection perpendicular to this direction. The long side surfaces 110 aand 110 b of the battery module 110 mounted on the holding spacer 130contact these cooling path forming projections 141, so that a coolingpath is formed between the long side surfaces 110 a and 110 b and thespacer body 131. On the other hand, a sheet-shaped heat generatingstructure is embedded in the spacer body 131 so that the battery module110 can be heated by the heat of the sheet-shaped heat generatingstructure.

FIG. 3 is an outer appearance view of FIG. 2 viewed from direction B.FIG. 4 shows an A-A cross section of FIG. 2. The battery module 110 isheld by the holding spacer 130 between adjacent battery modules 110 anda cooling path 210 is formed between the spacer body 131 and the batterymodule 110 by the cooling path forming projections 131 provided on thespacer body 131 of the holding spacer 130. A coolant is circulatedthrough the cooling path in the direction B of FIG. 2, and the batterymodule 110 is cooled. A sheet-shaped heat generating structure 200 isembedded in the spacer body 131, as shown by a broken line in thefigures, and heat is generated by applying electricity through thesheet-shaped heat generating structure. The sheet-shaped heat generatingstructure 200 is embedded over approximately the entire surface of thespacer body 131. In addition, the sheet-shaped heat generating structure200 is embedded at an approximate center position of the spacer body 131so that the distances to adjacent battery modules 110 are almost equal.Because the cooling path forming projections 141 projecting from thespacer body 131 are in contact with the long side surfaces 110 a and 110b of the battery modules 110, the heat from the sheet-shaped heatgenerating structure is efficiently conducted to the battery module 110through the cooling path forming projection 141 and the battery module110 is quickly heated. In addition, the cooling path 210 extends along avertical direction Z and the battery module 110 is quickly and uniformlyheated by heat convection through the cooling path 210. For thesheet-shaped heat generating structure 200, an arbitrary material whichis heated by applying electricity, such as a resistor and asemiconductor, may be used.

Control of the application of electricity to the sheet-shaped heatgenerating structure may be automatic or may be manual. For example, atemperature sensor may be provided at a predetermined position of thebattery pack, electricity may be applied to the sheet-shaped heatgenerating structure 200 when the temperature detected by thetemperature sensor is less than or equal to a predetermined temperature,and the electricity application may be stopped when the detectedtemperature becomes greater than or equal to a predeterminedtemperature. The battery module 110 desirably has a temperature which isgreater than or equal to a predetermined temperature and the temperaturedistribution among the plurality of battery modules 110 placed in thebattery pack is desirably uniform. Therefore, it is desirable to detecta temperature distribution of the battery modules 110 in the batterypack with a plurality of temperature sensors provided at a plurality ofpredetermined positions of the battery pack, and to stop the electricityapplication when the temperature is greater than or equal to apredetermined temperature and the temperature distribution becomesuniform.

Alternatively, the electricity may be applied to the sheet-shaped heatgenerating structure 200 by a user of the vehicle such as an electronicvehicle or a hybrid electric vehicle on which the battery pack isequipped manually operating a switch in the cold climate. For theelectric power to be applied to the sheet-shaped heat generatingstructure 200, for example, a commercial power supply may be used. In acold climate, when the vehicle is parked in a garage of the user's home(no coolant flows in the cooling path), the vehicle may be connected tothe commercial power supply through a plug, and electricity may beapplied to the sheet-shaped heat generating structure 200 by theelectric power from the commercial power supply. With thisconfiguration, as each battery module can be heated even under alow-temperature environment, a superior output can be obtained as apower supply of the vehicle at the time of startup of the vehicle.

In the above-described preferred embodiment, a configuration isexemplified in which the sheet-shaped heat generating structure 200 isembedded in the spacer body 131. In this structure, the holding spacer130 and the sheet-shaped heat generating structure 200 are integrated.Alternatively, a configuration may be employed in which the holdingspacer 130 and the sheet-shaped heat generating structure 200 areseparated. FIG. 5 shows the holding spacer 130 of a separated type. Thespacer body 131 of the holding spacer 130 is separated into twocomponents, and the cooling path forming projections 141 are formed on asurface of each component. The sheet-shaped heat generating structure200 is placed between the two separated components of the spacer body131.

FIG. 6 shows another structure of the holding spacer 130 having a heatgenerating function. FIG. 7 is an outer appearance view of FIG. 6 viewedfrom direction D and FIG. 8 is a C-C cross sectional view of FIG. 6. Theholding spacer 130 which is an electrically insulating structure has thecooling path forming projection 141 which projects in a direction ofplacement Y of the battery modules 110. The cooling path formingprojection 141 has a hollow polygonal column shape and extends along avertical direction Z, projects from the spacer body 131, contacts thelong side surfaces 110 a and 110 b of the battery module 110, and holdsthe battery module 110. In addition, a gap is provided between theadjacent cooling path forming projections 141 having a hollow polygoncolumn shape, and a cooling path 210 is formed by the gap. The spacingbetween the hollow polygon column-shaped cooling path formingprojections 141 is, for example, approximately the same as the spacingbetween the cooling path forming projections 141 shown in FIG. 2. Thecooling path forming projection 141 of the present embodiment can beconsidered as a structure obtained by connecting a plurality of coolingpath forming projections 141 provided along a vertical direction shownin FIG. 2, and making the inside hollow.

A linear or a tubular heat generating structure 202 is inserted into thehollow portion of the hollow polygon column-shaped cooling path formingprojection 141. The battery module 110 is heated by applying electricityto the inserted linear or tubular heat generating structure 202. In thepresent embodiment also, because the hollow polygon column-shapedcooling path forming projections 141 are in contact with the long sidesurfaces 110 a and 110 b of the battery modules 110, the heat from theheat generating structure 202 can be efficiently conducted to thebattery module 110 through the hollow polygon column-shaped cooling pathforming projection 141, and the battery module 110 can be quicklyheated. The size of the linear or tubular heat generating structure 202is desirably set to be approximately identical to the size of the hollowportion. The linear or tubular heat generating structure 202 can befreely inserted into and taken out from the hollow portion of thecooling path forming projection 141. Therefore, it is not necessary toprepare, as the battery pack, two separate types of battery packsincluding a normal specification equipped with the holding spacer whichdoes not have the heat generating structure and a cold climatespecification equipped with the holding spacer having a heat generatingstructure integrally formed with the holding spacer, and the batterypack may be easily changed to the cold climate specification byinserting the heat generating structure 202 into the hollow portion ofthe spacer body 131 of the battery pack of the normal specificationequipped with the holding spacer which does not have the heat generatingstructure.

As described, in the present embodiment, by adding the function to heatthe battery module 110 to the functions of the holding spacer 130 tohold the battery module 110 and to form the cooling path for cooling thebattery module 110, it is possible to quickly heat the battery module110 and prevent performance degradation in a low temperature environmentwhile preventing increase in the number of components.

The present invention is not limited to the above-described preferredembodiment, and other configurations may be employed.

For example, in the preferred embodiment, as shown in FIGS. 3 and 4, onesheet-shaped heat generating structure 200 is placed in the spacer body131, but the number of the sheet-shaped heat generating structure 200does not need to be 1, and a plurality of sheet-shaped heat generatingstructures may be embedded in the spacer body 131 in a predeterminedplacement relationship. For example, band-shaped heat generatingstructures may be placed with a predetermined spacing.

In addition, in the preferred embodiment, as shown in FIGS. 3 and 6, theheat generating structure is placed in the spacer body 131.Alternatively, the heat generating structure may be provided on thesurface of the spacer body 131. For example, the heat generatingstructure may be provided on the contact surface of the cooling pathforming projection 141 with the battery module 110 in FIG. 2. Morespecifically, a sheet-shaped heat generating structure of a strip shapemay be adhered or welded on the cooling path forming projection 141extending in a straight line shape in a direction Z perpendicular to thedirection of placement of the module. Of the surfaces of the spacer body131, it is also possible to provide the heat generating structure on thesurface forming the cooling path 210. In this case, the size of the heatgenerating structure is desirably inhibited to a degree to notsignificantly increase the flow path resistance of the cooling path 210.In other words, it is sufficient to not provide the heat generating unitseparately from the holding spacer 130, but rather, provide the heatgenerating unit integrally with the holding spacer 130, morespecifically, on a surface of the inside of the holding spacer 130.

In the preferred embodiment, although a sheet-shaped heat generatingstructure 200 or a linear or tubular heat generating structure 202 isused as the unit for heating the battery module 110, the shape is notlimited. In addition, in a cold climate, the battery pack has a lowertemperature at an outer position with respect to an axis of symmetry,that is, at a more peripheral section than the center section of thebattery pack. Therefore, the shape of the heat generating structure maybe changed such that the amount of heat generation at the peripheralsection of the battery pack is greater than that of the center section.For example, the placement area of the sheet-shaped heat generatingstructure 200 may be increased for the peripheral section or the linearor tubular heat generating structure 202 may be narrowed at theperipheral section. Alternatively, the same shape may be employed forthe heat generating structure, and the applied current may be increasedat the peripheral section. Moreover, the holding spacer 130 is formedwith an electrically insulating resin, and it is preferable to addcalcium oxide, titanium oxide, silicon oxide, zinc oxide, siliconnitride, aluminum nitride, etc., in the resin to achieve a heatconductive characteristic.

1. A battery pack comprising: a plurality of battery modules; and aholding spacer which is placed between the battery modules and holds thebattery module, wherein in the holding spacer, a plurality ofprojections which contact the battery module and hold the battery moduleare formed, a cooling path through which a coolant is circulated isformed in a part where the projection is not formed, and a heatgenerating unit which heats the battery module is provided.
 2. Thebattery pack according to claim 1, wherein the heat generating unit isembedded in the holding spacer.
 3. The battery pack according to claim1, wherein a hollow section is formed in the holding spacer, and theheat generating unit is inserted into the hollow section.
 4. The batterypack according to claim 3, wherein the projection of the holding spaceris a hollow column-shaped projection which extends in a directionperpendicular to a direction of placement of the battery modules.
 5. Thebattery pack according to claim 1, wherein the heat generating unit hasa greater amount of heat generation at a peripheral section of thebattery pack than at a center section of the battery pack.
 6. Thebattery pack according to claim 1, wherein the battery module has arectangular parallelepiped shape including a plurality of cells placedin a line.
 7. The battery pack according to claim 6, wherein the batterymodule and the holding spacer are integrated by being sandwiched by endplates at both ends and restrained overall by a restraining unit.